Inspection tools that use EUV light cannot use a particle protection device, such as a pellicle, that may be used with inspection tools utilizing light with longer wavelengths. In EUV inspection systems, any particle on the reticle surface will cause unacceptable problems. Several particle protection mechanisms have been proposed to protect the reticle from particles generated from inspection optics that send the inspection EUV light to the reticle, generally via a central hole in a plate proximate the reticle. A second source of particles is the movable stage that moves the reticle during the inspection process.
Prior methods do not protect inspection systems from particles as small as 10 nm in diameter or they have been used in processes in which reticles are cleaned after inspections. However, with EUV inspection systems, while no cleaning is possible, particles as small as 10 nm must still be removed.
U.S. Pat. No. 7,875,864 to Sogard describes a particle protection system that combines a thermophoresis device and electrophoresis device. However, the thermophoresis device tends to heat the reticle thereby causing distortions in the reticle itself.
What is needed in the field is an apparatus, system, and/or method to protect the reticle of EUV inspection systems from particles with a diameter of 10 nm and greater.